The invention relates to an access card having encoded material as generically defined by the preamble to claim 1.
Access cards, according to the invention, provide the card holder with a code word that is not readily decipherable, with which either the card holder only or a number of card holders provided with the same code word, gains access, once the code word has been read out to some apparatus that can be unlocked only with the correct code word; the prerequisite is the possession of the appropriate access card. The use of infrared light to decipher the code prevents unauthorized used by switching off the short-wave radiation of visible light. Furthermore, the available technical infrared radiation emitters and receivers, even with the capacity required, are so small that they can be used together with electronic circuits, for instance being built into the locks of doors.
Accordingly, one example of a practical application of the invention is so-called key cards which are given to hotel guests instead of metal keys, and with which the lock of a hotel room is opened. These key cards are incomparably less expensive than conventional room keys and thus prevent the very considerable financial losses incurred by hotel owners and others when hotel guests intentionally or unintentionally fail to return their room key and instead take them along when they leave, or lose them. In these cases, as a rule, it is not enough merely to replace the lost key and have the usually locked hotel room opened by a locksmith. Instead, once opened, the lock must be removed and replaced with a new one to prevent subsequent unauthorized access. If the hotel owner uses key cards instead, then if they are lost there is practically no financial loss as a result. Furthermore, the door locks are embodied such that they can be reset for different code words. Thus, it becomes unnecessary to replace the lock if the key card is lost.
The invention is based on a previously known access card which is used, among other applications, in a system of the above-described special type. The code comprises a sequence of perforations in the card through which, in the lock, the beam of a built-in infrared emitter passes and strikes a receiver which uses an electronic circuit to decipher the code and then either opens the lock or keeps it closed. However, unauthorized use cannot be pecluded with these cards because the punch code is visible, and even without knowing the code word a counterfeiter can readily copy the code onto a counterfeit card, which need merely be a correspondingly perforated foil or film blank.